1. Field of the Invention
The invention relates to a vehicle pop-up hood apparatus that lifts an engine hood under predetermined conditions.
2. Description of the Related Art
In a vehicle pop-up hood apparatus in which a hinge arrangement disclosed in WO01/23226A1 is used, a bonnet (engine hood) is connected to a body through a hinge mechanism. In the hinge mechanism, one end of a middle leaf (link member) is connected to a body-side lower leaf so as to be pivotable about a first pivot, and the other end of the middle leaf is connected to a bonnet-side upper leaf so as to be pivotable about a second pivot. The upper leaf and the middle leaf are integrally connected to each other through a clip mechanism. Under normal conditions, the middle leaf pivots about the first pivot when the bonnet is opened or closed.
When an air bag disposed further forward than the link mechanism and below the bonnet is activated, an air bag deploys, and the bonnet receives the lifting force from the bag, the connection between the upper leaf and the middle leaf by means of the clip mechanism is broken, and the bonnet ascends in a manner such that the bonnet pivots about a front end latch.
When the bonnet is opened under normal conditions, a locking means, such as a latch, for securely coupling the bonnet and the vehicle body on the front-end side of the bonnet is released, and the bonnet its caused to pivot about an axis on the rear-end side thereof by lifting the front-end side of the bonnet. Accordingly, the center of pivotal movement of the bonnet in this case is the first pivot that connects the lower leaf and the middle leaf. On the other hand, when the deploying air bag lifts the bonnet, the secure coupling between the bonnet and the vehicle body by means of the locking means is not released. Thus, the center of pivotal movement of the bonnet in this case is on the front-end side of the bonnet.
As described above, depending on whether the bonnet is opened under normal conditions, or is lifted by the deploying air bag, the center of the pivotal movement of the bonnet varies, and naturally, the trajectory of the pivotal movement of the bonnet varies. When the air bag lifts the bonnet, the bonnet can be drawn toward the rear of the vehicle, and the above locking means can be therefore deformed, due to the difference in the trajectory of the pivotal movement. When the resistance to deformation is high on the front-end side of the bonnet, including the locking means, and the bonnet does not move toward the rear, the first pivot and the second pivot are drawn toward the front of the vehicle, and therefore, the bonnet cannot be sufficiently lifted.